Jump to content
Sign in to follow this  
Followers 0
Save Old Iron

How To - Test a Diode

By Save Old Iron, in Electrical

Recommended Posts

Save Old Iron    1,568

Save Old Iron
Posted

Please note the position of the "band" on the diode and what color lead (positive / red or negative / black) is connected banded lead of the diode. Diodes are the equivalent of check valves in the world of plumbing or hydraulics. Current should only flow in one direction thru the diode. Current flow should be present when the negative / black lead of the multimeter is connected to the banded lead of the diode and the positive / red lead is connected to the opposite lead. 

 

(click on image to enlarge)

diodetesting_zpsfb82f8c3.gif


The diagram below shows a defective diode that has an internal short circuit in the body of the diode. The diode no longer has a "one way" characteristic and acts as if it were a piece of wire - current will flow in either direction thru the shorted diode so meter lead orientation makes shows no difference. In the world of plumbing or hydraulics, the check valve would be "stuck open".

diodetestingshorted_zpsca06286e.gif


The defective diode below is the equivalent of a burned out fuse. No current can flow thru the diode in either direction. The meter readings show a high resistance to current flow in either lead orientation. The hydraulic equivalent would be a check valve was "stuck closed".

diodetestingopen_zps50f158bd.gif

  • Like 1

Share this post

Link to post
Share on other sites
 

Tinhorse    0

Tinhorse
Posted

Just think of a diode as a one way check valve for the flow of electrons.

Share this post

Link to post
Share on other sites
 

Thunderlizard    1

Thunderlizard
Posted

Great post!  and to add...

 

...which is why LED's are polarized (only work when hooked in correct polarity). ( Light Emitting Diodes. :-)  )

Share this post

Link to post
Share on other sites
 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
Followers 0
Go To Topic Listing

  • Similar Content

    • WheelPuke
      89 400 series 25A fuse blowing
      By WheelPuke
      I have my 25A fuse blowing every time I put a new one in the slot. The old one was burnt up when I got the tractor put this year. It sat for a year with a dead battery. I stopped using it as much because the transmission is clattering pretty bad when taking off on second or higher. I had to replace the clutch belt a few years ago and couldn't get an OEM. Not sure what is the problem there that's another issue though.
       
      I have checked the wiring and patched the worn spots where it could be grounding out. The fuse blows as soon as there is power to the system with the ignition off. I'm at a loss of what to check for at this point. Any input from someone who has had this issue would be appreciated. I'm not sure what these units are in the photos but do not know how to test them for a failure. They are directly in loop with the battery and the ignition loom looks to run into that 25A fuse.

    • Deer hunter
      Kohler K-19 Engine search
      By Deer hunter
      Does anyone know where I could find a complete engine rebuild kit from for the k-19 ? I absolutely love my c-195 and have had it for years. But the motor let go last fall and I want to rebuild it or upgrade the motor, any suggestions?
    • davidfindlay
      1984 C Series, dump trailer and leaf impeller
      By davidfindlay
      Looking to find a new home for my 84 (I think) C-145. It has a dump trailer with the enclosure for leaves, the PTO impeller to get the leafs into the trailer, the hoses for deck-to-impeller, impeller-to-trailer.
       
      I haven’t run it in over a year.
      The battery and the cable to the battery probably need to be replaced.
      Comes with a new head gasket still in the bag.
      Seat is cracked but still comfortable.
       
      Happy to answer questions or take other pictures.















    • BrianStasC-101
      predator 420 pto
      By BrianStasC-101
      Hello all. I am looking for suggestions on adapting the pto from my C series tractor to a harbor freight predator 420 13hp engine. I know the predator motors are a controversial topic however it is the route I have chosen for this particular machine. The intent was to mostly use it for plowing so no PTO required but it would be handy to have. Looking to hear from someone that has successfully done the swap that may offer any advice before I attempt to transfer it over. Just looking for any general pointers that will help me along the way to make it go as smoothly as possible. 
    • HumbleHans
      Tractor 1984 C -Series OM Wiring Rev.pdf
      By HumbleHans
      Operator manual 810343R1
      Wiring
      34 pages 17.5MB
       
      Wiring Colored 
      1 page 228KB
       
      1984 C-105 8-Speed model 11-10K802
      1984 C-125 8-Speed model 11-12K802
      1984 C-145 Automatic model 11-14KE01 - Some used alternate inner axle bearing See PSB #369
      1984 C-165 8-Speed model 11-16K801
      1984 C-175 Twin Automatic model 11-17KE01 - Some used alternate inner axle bearing See PSB #369
      1984 C-195 Twin Automatic model 01-19KE02
       
       
×
×
  • Create New...